A variety of elastomeric polymers are known in the art. By way of illustration, polyurethane elastomers made from polyols prepared using a double metal cyanide complex catalyst are known, as illustrated by U.S. Pat. No. 5,096,993 which discloses the production of thermoplastic ("TPU") elastomers made using DMC-prepared polyether polyols. These elastomers are disclosed in the '993 patent as having excellent physical and chemical properties.
One particular elastomeric polymer in fiber form, namely spandex, is a well-known component of clothing, particularly sportswear, which adds elasticity to the clothing. Spandex is, by definition, a hard-segment/soft-segment-containing, urethane-containing polymer composed of at least 85% by weight of a segmented polyurethane(urea). The term "segmented" refers to alternating soft and hard regions within the polymer structure. Formation of the segmented polymer structure takes place in several discrete steps. The first step involves the formation of linear polyester or polyether macroglycols typically having molecular weights of between about 500 and about 4000 and having isocyanate reactive hydroxyl group at both ends of the macroglycol molecule. The next step involves the reaction of the macroglycol with an excess of an isocyanate, typically in about a 1:2 molar ratio, to form an isocyanate-terminated soft segment prepolymer. The hard segments are formed next by reacting the isocyanate-terminated prepolymer with low molecular weight glycols or diamines. The resulting hard segments provide sites for hydrogen bonding and act as tie points in the segmented polyurethane responsible for long-range elasticity. As an alternative to the prepolymer method, a "one-shot" method is suitably used to produce the desired elastomeric polymer for subsequent processing to produce spandex fibers by melt spinning.
Spandex fibers are suitably prepared by extruding the urethane or urethane precursor through a spinnerette into a diamine bath where filament and polymer formation occur simultaneously, as disclosed, for example, in U.S. Pat. No. 4,002,711.
The current polyol of choice in the manufacture of spandex is poly(tetramethylene ether glycol) ("PTMEG") and the utilization of PTMEG in the preparation of spandex is disclosed, for example, in U.S. Pat. No. 5,185,420. Unfortunately, PTMEG is more expensive than might be desired, and the physical properties of the resulting spandex leave room for improvement, particularly with respect to strength and thermal and hydrolytic stability properties.
The present invention provides a method to achieve these excellent strength and stability properties at a cheaper cost than is associated with the use of PTMEG polyols.